A History of Horns

[Altec Best]

That's a really great resource and a good read. But I wish for the sake of completeness he'd included a picture of the Chrysler Air Raid Siren.

VictorySiren.com - Internet Home for the Chrysler Air Raid Siren

Air coming out of the horn is moving @ 400 mph ! 176 db @ the siren 138 db @ 100 ft. and can be heard over 10 miles away ! It uses a 331 cu Hemi. That is pretty far.

http://chryslerairraidsiren.com/